丹江口水库一株硅藻的分子鉴定及氮素对其生长的影响

Molecular identification of a diatom from Danjiangkou reservoir and the effects of nitrogen on its growth

采用稀释分离法和小液滴分离法,从丹江口水库水样中分离了一株硅藻。通过形态学观察和18S rDNA、SSU rDNA、rbcL的序列分析,将其鉴定为谷皮菱形藻。以NaNO_(3)、NH_(4)Cl和尿素为氮源,研究了不同氮素对其生长特性的影响。结果表明,谷皮菱形藻在铵态氮、硝态氮和有机氮中均可正常生长,但生长特性对不同氮素形态的响应有所不同。在NaNO_(3)和尿素的培养条件下,谷皮菱形藻的生长速率随氮素浓度的增加而相应增加,而在NH_(4)Cl培养基中,生长速率随氮素浓度的增加表现出先增加后降低的趋势。在NH_(4)Cl 350μmol·L^(-1)时达到最高,最大比生长速率和细胞密度分别为0.2920 d^(-1)和189×10^(4)个·mL^(-1),表明高浓度铵态氮对其生长有抑制作用。本研究可为谷皮菱形藻的分子鉴定提供依据,也可为保护丹江口水库的水质安全提供基础资料。

A strain of diatom was isolated from water samples in Danjiangkou reservoir using dilution separation and small droplet separation methods.Based on morphological observation and homologous analysis of 18S rDNA,SSU rDNA,and rbcL sequences,the strain of diatom D0710 obtained from Danjiangkou reservoir was identified as Nitzschia palea.The growth of N.palea was investigated using sodium nitrate,ammonium chloride and urea as nitrogen source,respectively,and the effects of nitrogen on its growth were determined.The results showed that the strain of N.palea grew normally in sodium nitrate,ammonium chloride and urea medium,but the responses to different nitrogen forms were quite different.In sodium nitrate and urea medium,the specific growth rate and the cell density of N.palea increased with increment of nitrogen concentration.Under ammonium chloride culture condition,the growth rate of N.palea increased firstly and then reduced as nitrogen concentration increased in culture medium.The specific growth rate and the cell density were 0.2794 d^(-1)and 189×10^(4)cells·mL^(-1),respectively,when N.palea was supplied with 350μmol·L^(-1)of ammonium chloride.The results suggested that high concentration of ammonium as nitrogen source inhibited the growth of N.palea.This study provided not only an experimental basis for the molecular identification of N.palea in fresh water column,but also basic data for water quality protection and ecosystem management in Danjiangkou reservoir.